<template>
    <ul class="list">
        <li class="item" v-for = "item of letters"
            :key="item"
            :ref="item"
            @click="handleLetterClick"
            @touchstart="handleTouchStart"
            @touchmove="handleTouchMove"
            @touchend="handleTouchEnd"
            >{{item}}</li>
    </ul>
</template>

<script>
import Bscroll from 'better-scroll'
    export default{
        name:"CityAlphabet",
        props:{
            cities:Object
        },
        computed:{
            letters (){
                const letters = []
                for(let i in this.cities){
                    letters.push(i)
                }
                return letters
            }
        },
        data (){
            return {
                touchStatus:false
            }
        },
        methods:{
            handleLetterClick(e){
                this.$emit('change',e.target.innerText)
            },
            handleTouchStart(){
                this.touchStatus = true
            },
            handleTouchMove(e){
                if(this.touchStatus){
                    const startY = this.$refs['A'][0].offsetTop
                    const touchY = e.touches[0].clientY-90
                    const index = Math.floor((touchY-startY)/20)
                    if(index>=0 && index<this.letters.length){
                        this.$emit('change',this.letters[index])
                    }
                }
            },
            handleTouchEnd(){
                this.touchStatus = false
            }
        }
    }
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.list
    display flex
    flex-direction column
    justify-content center
    position absolute
    top 1.58rem
    right 0
    bottom 0
    width 0.4rem
    .item
        line-height 0.44rem
        text-align center    
        color $bgColor
</style>
